1. Field of the Invention
The invention relates to steam heated dryer drums in a paper machine and more particularly to a flow control system for controlling the flow of steam through a dryer using a positive displacement pump to create differential and condensate evacuation from the paper machine dryers.
2. Brief Description of the Prior Art
For many years the advantages of flow control for dryer drainage systems have been known and discussed. U.S Pat. No. 2,869,248 discloses a device for controlling the flow of steam through a dryer drum in a paper machine. U.S. Pat. No. 2,992,493 discloses a dryer and drainage system by providing a flow control on the downstream side of the drying rolls which operates to automatically maintain the steam flow through each of the rolls or cylinders at a predetermined minimum quantity regardless of the varying load conditions on the rolls. Use of an orifice plate is an absolute necessity in the prior state of the art.
The present invention embodies a positive displacement pump (gas pump) which gives the system distinct advantages and benefits not found in the systems of the prior art. None of such prior art systems employ positive displacement pumps. The pump used herein is a conventional rotary positive blower of the type developed by the Roots brothers and sold by several manufacturers.